title: Pilot-scale fluoride-containing wastewater treatment by the ballasted flocculation process.
abstract: A pilot-scale ballasted flocculation system was used to remove fluoride from one type of industrial wastewater. The system included the formation of calcium fluoride (CaF2) using calcium hydroxide followed by coagulation sedimentation. Calcium fluoride was recycled as nuclei for enhancing CaF2 precipitation and as a ballasting agent for improving fluoride removal and flocculation efficiency. Factors affecting fluoride and turbidity removal efficiencies, including pH in the CaF2-reacting tank and coagulation-mixing tank, sludge recycling ratio, and dosages of FeCl3 and polyacrylamide (PAM), were investigated in the pilot-scale system. The recycled CaF2 precipitates improved CaF2 formation kinetics, enhanced fluoride removal and flocculation performance. Under the optimized condition, the ballast flocculation process reduced fluoride concentration from 288.9 to 10.67 mg/L and the turbidity from 129.6 NTU to below 2.5 NTU.
authors.affiliation: State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.
authors.forename: Bin-Yuan
authors.initials: BY
authors.lastname: Wang
authors.forename: Zhong-Lin
authors.initials: ZL
authors.lastname: Chen
authors.forename: Jia
authors.initials: J
authors.lastname: Zhu
authors.forename: Ji-Min
authors.initials: JM
authors.lastname: Shen
authors.forename: Ying
authors.initials: Y
authors.lastname: Han
mesh_terms: D002124:Calcium Fluoride / Q000032:analysis; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D002124:Calcium Fluoride